[Wien] Query about SOC in WIEN2k

[Xavier Rocquefelte]

Dear R. Chouhan

Just to complete the very nice answer of Peter. I have used the force 
theorem as explained by Peter using GGA+U to estimate MCA and in the 
cases I have considered it works amazingly nicely.

As Peter said, I was using P1 symmetry and checking carefully the 
convergency before including the spin-orbit effect along specific 
directions.

Here is an example of what we obtained for CuO (Fig. 3). Similar results 
are obtained using on-site hybrid of GGA+U.

http://www.nature.com/articles/ncomms3511

Best Regards

Xavier


Le 05/11/2016 à 17:43, Peter Blaha a écrit :
> There are a lot of problems in your calculations:
>
> Usually the energy difference between 2 such calculations is extremely 
> small and one must be very careful to get meaningful numbers.
>
> When you do initso  for a spinpolarized system, the symmetry can be 
> reduced. In such cases you MUST take the newly generated struct file.
>
> > Do you want to use the new structure for SO calculations ? (y/N)   N
>
> This is the wrong answer !
>
> In fact, one should even do the calculations for the different 
> magnetization directions with the same symmetry (eventually in P1). 
> Thus checkout what symmetries you get for the different directions and 
> choose the one which is compatible with all cases.
> Check your case.inorb/dmc files in case that the number of atoms has 
> been changed.
>
> Important:
> Increase Emax in case.in1 to a VERY large number (10 Ry), and test 
> your results with respect to this EMAX.
> Increase the k-mesh (for the final low-symmetry struct file) to a very 
> good one AND TEST the convergence. of your results.
>
> With such a struct file you run again (in the same directory) the 
> non-so calculation to selfconsistency with a good k-mesh and good 
> convergence:
> runsp -orb -ec 0.000001 -cc 0.000001
>
> Since the E differences are very small, set the DEs  in case.in1 to a 
> smaller value like:
> 0   -4.09      .0001 STOP 1
>                ^^^^^^^  DE
>
> Once the non-so calculation is converged:
>
> save_lapw non_so
>
> Now the force theorem:
> select  001 direction in case.inso
> x lapw1 -up/dn
> x lapwso -up -orb
> x lapw2 -so -up/dn
> cp case.scf2up/dn 001_kmesh_emax.scf2up/dn
>
> select other direction(s) and repeat the above steps.
> Compare the band energies listed in the scf2xx files.
>
> for the energy:
> select 001 direction
> runsp  -so -orb -ec 0.000001 -cc 0.000001
> save 001_kmesh_emax
>
> restore non_so
> do everything again for another direction.
>
> Make sure to check EMX and kmesh convergence.
>
> PS: I've never done MCA calculations using GGA+U !!
>
> Am 05.11.2016 um 06:26 schrieb Rajiv Chouhan:
>> Dear Dr. P. Blaha,
>>
>> I am trying to calculate the magnetic anisotropy energy (MAE) for the
>> magnetic system Nd-metal. For this I tried couple of methods (energy
>> theorem and force theorem) to calculate MAE.
>>
>> Energy theorem:
>>
>> step-1: Performed GGA+U ; Step-2: executed initso_lapw  for different
>> directions 001, 100 etc ; Step-3: Didn't put RLO (relativistic local
>> orbital in the .inso file)
>>
>> Step-4: Performed runsp_lapw -so -orb -dm  -ec 0.000001 ; Step-5 Took
>> the difference of energies E[001] - E[100]
>>
>> The above method give correct result in very few cases. Am I doing wrong
>> somewhere?
>>
>>
>> Force Theorem:
>>
>> Will you please explain the steps correctly because I am confused while
>> doing the steps. I followed the below steps and this is not working 
>> for me.
>>
>> Step-1: Performed GGA+U (runsp_lapw -dm -orb -ec 0.000001);
>>
>> Step-2: initso_lapw (by taking below actions)
>>
>> ---->Add RLO for NONE, ALL, CHOOSE elements? (N/a/c) : N
>>
>> Do you have a spinpolarized case (and want to run symmetso) ? (y/N) Y
>>
>> Do you want to use the new structure for SO calculations ? (y/N)   N
>>
>> Step-3: x lapwso -up
>>
>> Step-4: x lapw2 -up
>>
>> Step-5: x lapw2 -dn
>>
>> Step-6:  MAE = 001(sum of eigenvalues up & down) - 100(sum of
>> eigenvalues up & down)
>>
>> This force method is also not working properly. Will you please correct
>> me where I am doing wrong.
>>
>> I also followed the following links for my above steps:
>>
>> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09408.html 
>>
>>
>> http://zeus.theochem.tuwien.ac.at/pipermail/wien/2010-September/013730.html 
>>
>>
>> Thank you,
>> R. Chouhan
>>
>>
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>